The girls were all friends, police in Charlestown say. Then, one evening in February, three of them attacked a fourth. They punched her, pulled her hair, and as she lay defenseless, prosecutors said, one of the girls, 17-year-old Samantha Owen, stole $30 from the girl’s purse.

It was just one of a roster of violent crimes by girls in recent months, punctuated last week by horrific allegations that 17-year-old Samia Jones
used a butcher knife to repeatedly stab a young mother in the Savin Hill section of Dorchester.

City officials, alarmed by a string of high-profile cases and by what they say is a worrisome climate of fear among girls in some neighborhoods, are launching a public service campaign aimed at girls who may be headed toward violence.

“This is an issue,” said Marie St. Fleur, a top aide for Mayor Thomas M. Menino on urban issues who is leading the campaign. “We are trying to get our arms around it.”

The effort involves a marketing blitz of positive messages in neighborhoods such as Dorchester and Roxbury that will include billboards and posters, as well as posts on social media.

The main perpetrators — and targets of youth violence prevention efforts — have long been at-risk boys in troubled areas; a $10 million statewide antiviolence measure announced two years ago specifically targeted males ages 14 to 24.

Local ministers and youth advocates say some girls have been fueling gang feuds and staging fights that are posted on YouTube and Facebook. Recent surveys of teen girls by officials looking to address educational gaps and health issues, such as sexually transmitted diseases, discovered girls in some neighborhoods named violence as a key issue.

Boston police data show violent crimes among females 13 to 24 fell from 408 in 2008 to 217 in 2012. And the state Department of Youth Services had a peak of 514 troubled girls in its care in 2003, but just 190 in 2011 and 100 so far this year, said commissioner Edward Dolan.

But officials and advocates who work with girls say that on the street, they are hearing a different message.

“If you talk to young girls they will tell that there is violence,’’ said St. Fleur. “I don’t walk in their shoes on a day-to-day basis, but they have to navigate the communities they are in right now. . . . When we talked to the girls, public safety and violence were among the top things they talked about. ”

Recent examples include a 15-year-old Hyde Park girl who was arrested last month after police alleged that she was among a mob who beat up an MBTA driver at a bus stop on Columbia Road in Dorchester.

Mercedes Reyes, 17, said it is tough to be a girl in Uphams Corner. Not only does she have to deal with the indignity of catcalls from boys driving by in cars, but she has to walk a fine line with girls as well. “Sometimes they just
. . . mess with you for no reason,” she said.

And some girls, said 17-year-old Precious Natal, “like to threaten other girls.”

Girls have traditionally committed fewer crimes than boys, but some youth advocates say that girls have been the source of jealousy that has caused violence between rival teen males.

“Males in conflict will use the girls as pawns,’’ said Sheri Bridgeman, director of programs at the Center for Teen Empowerment, a local nonprofit. “They are being used and are caught in the middle.”

St. Fleur said fights in Dudley Square, the triple homicides last year, and the stabbing near Savin Hill train station are all examples of the need for youth advocates to unite around girls to keep them out of trouble. Here the city is mobilizing 30 community groups that work with girls to help in the effort.

The girls’ campaign, still in its infancy, is focusing on the so-called ”Circle of Promise,” a city-designated swath of Dorchester, Roxbury, and other neighborhoods long mired in poverty, crime, and teenage pregnancy.

In the next few weeks, St. Fleur and aide Ramon Soto will hold community meetings, brainstorming sessions, and talk with girls about how to shape the campaign’s message. Girls involved in Girlz Radio, a Dorchester-based Internet station, and at the Holland and Marshall community centers are also helping.

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